Sen. John McCain (R-Ariz.) said last week that he has privately warned fellow GOP Senators not to go overboard in blocking President Barack Obama's nominees — noting it could hurt a future Republican president.

"I have talked to my colleagues," McCain said. "For example, there is a candidate for the secretary of Commerce who wouldn't have been my choice, OK? But the president deserves to have his nominee unless there is a compelling reason not to. And I warn my colleagues, [if] you are going to vote against people just because you don't like them and they don't share your philosophy, you better be careful that that may happen to you when you have a Republican president."

McCain's comments came a few hours before the Senate confirmed John Bryson for the Commerce post on a 74-26 vote.

Nominations have long been a partisan battleground, but McCain's warning comes as Republicans look to retake the Senate and the presidency in 2012 amid some favorable political conditions.

Bryson's nomination had been held up by Republicans since May as leverage to get Obama to deal with free-tradeagreements long sought by the GOP. Other Republicans, including Sen. James Inhofe (Okla.), objected to Bryson on other grounds, citing his past as a co-founder of the environmentalist Natural Resources Defense Council.

Democrats have complained about other GOP-blocked nominations — ranging from judicial posts to more obscure ones, such as the public printer who heads the Government Printing Office — as well as Republican obstructionism on jobs bills and minor legislation on small businesses and economic development earlier this year.

Public Printer William Boarman was a recess appointment to the post last year after the GOP held up his nomination, first made in April 2010. But Republican Sens. Orrin Hatch (Utah) and Johnny Isakson (Ga.) are still blocking his confirmation because of an unrelated dispute over the nomination of a Republican to the National Labor Relations Board.

More than 40 Senate Republicans also pre-emptively vowed to block any nominee to head the new Consumer Financial Protection Bureau unless the Dodd-Frank financial reform law is amended to weaken the post.

Both sides have sparred over just how obstructionist the GOP has been — and whether Democrats will face blowback if they are in the minority because of Reid's penchant for trying to limit debate and for preventing votes on GOP amendments using a procedure known as "filling the amendment tree."

Sen. Mary Landrieu (D-La.) has long been known to hold nominations hostage — she delayed Office of Management and Budget Director Jacob Lew's confirmation for a month in an attempt get the administration's attention on an unrelated issue — but she said the GOP has taken it to an extreme. She called some of the GOP Members "mad scientists" for dreaming up new methods of obstruction.

Sen. Dianne Feinstein (D-Calif.) said she believes that Republicans have sown ill will.

"They have created a record for themselves. 'We won't let the president get the appointments he needs. We won't let the president fill the appellate circuit court bench. We are going to put holds on everything; hold hostage various things we don't like by putting a hold on an appointee.' When I came here that was never done," she said. "When I came here there were very few amendments on appropriations bills. Now you see people putting 60 or 70 amendments on a bill, and they know they are going to go down. It's kind of a show."

Sen. John Thune (R-S.D.) said Republicans take dilatory actions when they are left no other alternatives. He pointed to a recent move by Democrats to stop Republicans from employing a little-used motion that would allow the GOP to offer amendments after debate has been limited.

"What Reid did ... in terms of changing that precedent is something that might come back to bite them if they are ever in the minority again," Thune said.

Thune charged that Democratic leaders have sought to protect their Members from casting politically difficult votes, including on a budget resolution. He said the move has resulted in fewer opportunities for Republicans to have a say in crafting legislation.

"If they don't like the amendments we offer, [Reid] fills the tree, or says, 'You can have this many amendments, but I get to pick them,'" Thune said. "I don't think that is going to work around here. My view is that they could bear the brunt of some of the tactics that they have employed if they are ever in the minority, and we are back in the majority."

On judicial nominations, Sen. Chuck Grassley (R-Iowa) has repeatedly come to the floor to defend against charges of Republican obstructionism.

Two weeks ago, Grassley said Obama's circuit court nominees are being confirmed faster than President George W. Bush's were.

"I continue to be amazed and disappointed by the continuing allegations that Senate Republicans are delaying, obstructing or otherwise blocking judicial nominations," Grassley said.

He objected to Democratic charges that Republicans are requiring 60 votes on everything, including judges, noting that votes on only two judges this year have been subject to cloture votes. Grassley has also said that the Senate is working through a backlog of judicial emergencies created, in part, because the White House had been slow to nominate judges to fill vacancies.

A senior Senate Democratic aide said McCain's warning came amid other signs of discontent in the GOP ranks, citing Sen. Lamar Alexander's (Tenn.) decision to quit his No. 3 leadership post and the 11 Republicans who defied leadership's wishes and voted with Democrats to cut off debate on a China currencymanipulation bill.

"Democrats filibustered judicial nominees, blocked Cabinet secretaries throughout the Bush administration — and kept the Senate in pro-forma the last year of his term specifically to prevent appointments," the aide said. "They've never needed precedent to block Republican nominees."